1. Field of the Invention
This invention relates generally to a method and apparatus for analyzing and improving the quality and stability of digital communication systems. More specifically, this invention relates to analyzing and mitigating link failures and errors in a DSL system.
2. Description of Related Art
Digital subscriber line DSL) technologies provide potentially large bandwidth for digital communication over existing telephone subscriber lines (referred to as loops and/or the copper plant). Telephone subscriber lines can provide this bandwidth despite their original design for only voice-band analog communication. In particular, asymmetric DSL (ADSL) and very-high-speed DSL (VDSL) can adjust to the characteristics of the subscriber line by using a discrete multitone (DMT) line code that assigns a number of bits to each tone (or sub-carrier), which can be adjusted to channel conditions as determined during training and initialization of the modems (typically transceivers that function as both transmitters and receivers) at each end of the subscriber line. DSL systems can use vectoring technologies, where joint transmitter and/or joint receiver signal processing can be performed among multiple pairs to mitigate the effects of crosstalk interference, and thus to improve performance.
DSL systems would further benefit from determining the cause of DSL link instability and/or poor link quality that can lead to DSL link failures or link errors, and taking measures to improve link stability and/or link quality.